Method of making calcium nitrate explosive composition

ABSTRACT

An explosive composition and method is provided containing a mixture comprising calcium nitrate, a water miscible organic fuel and water.

United States Patent [191 Wilson et al.

[ June 11, 1974 METHOD OF MAKING CALCIUM NITRATE EXPLOSIVE COMPOSITION[75] inventors: John S. Wilson, Lake Jackson, Tex.;

Willard F. Clark; Thomas E. Slykhouse, both of Midland, Mich.

[73] Assignee: The Dow Chemical Corporation,

Midland, Mich.

[22] Filed: May 30, 1972 [21] Appl. No: 257,830

Related US. Application Data [62] Division of 561'. No. 34,522, May 4,1970.

[58] Field of Search 149/43, 41, 60, 61, 44, 149/46 [56] ReferencesCited UNITED STATES PATENTS 6/1969 Sheeran et al... 5/1972 149/61 x Clay149/61 x Primary Examiner-Stephen J. Lechert, Jr. Attorney, Agent, orFirm-Bruce M. Kanuch [5 7 ABSTRACT An explosive composition and methodis provided containing a mixture comprising calcium nitrate, a watermiscible organic fuel and water.

6 Claims, No Drawings METHOD OF MAKING CALCIUM NITRATE EXPLOSIVECOMPOSITION CROSS REFERENCE TO RELATED APPLICATION This application is adivision of application Ser. No. 34,522, filed May 4, 1970.

BACKGROUND OF THE INVENTION Inorganic oxidizing salt based explosivecompositions are well known in the art. Most of these compositionscontain ammonium nitrate as the major inorganic oxidizing saltconstituent. Other salts havebeen thought of as less potent or sosensitive and unstable as to be dangerous. In some compositions, aportion of the ammonium nitrate has been replaced by other inorganicoxidizing salts such as, for example, sodium nitrate, calcium nitrate,certain perchlorates and other inorganic oxidizing salts. These optionalinorganic oxidizing salts have been employed for various purposes, suchas economy, fluidizing properties, sensitivity enhancement and the like.

These inorganic oxidizing salt based explosive compositions vary fromdry mixes to slurry mixtures containing water and/or other liquids, suchas glycols, fuel oils and the like. A typical dry mix known in the artis ANFO which contains ammonium nitrate and fuel oil. Typical slurryexplosive compositions contain inorganic oxidizing salts, normally amajor portion comprising ammonium nitrate, water, a fuel and/orsensitizer and a thickening agent.

It has also been proposed to employ, in amounts up to about 16 percentby weight of these compositions, various organic solvent compounds'assupplemental fuels and fluidizing agents, e.g., formaldehyde, ethyleneglycol and the like. Waterless slurries containing a liquid organic fuelas a solvent for ammonium nitrate or ammonium perchlorate basedexplosive composition having a density greater than 1.8 grams per cubiccentimeter, have also been suggested.

Specifically, in the past calcium nitrate has been considered as a lesspotent minor substitute for a portion of the ammonium nitrate in certaininorganic oxidizing salt based compositions.

An explosive composition has now been discovered comprising calciumnitrate, a water miscible organic fuel component and water. The uniquecomposition can be employed as an explosive, as an explosive additive,and as, a base mix for preparing other explosives. These novelcompositions have certain unique favorable characteristics over otherinorganic oxidizing salt based explosive compositions known in the art.Of the more important characteristics is better sensitivity and fluidityat lower temperatures, even without the presence of additionalsensitizers and fuels such as selfexplosives metals and the like. Alsothe compositions are characterized as being detonable at higherdensities and in smaller diameters than prior ammonium nitrate basedexplosives.

SUMMARY OF THE INVENTION The present invention comprises an explosivecomposition comprising from about to about 100 percent of a mixturecomprising, as percent by weight, calcium nitrate about 65-85 percent, awater miscible organic fuel about to about 35 percent, and water presentin an amount such that the ratio, by weight, of water in the mixture tocalcium nitrate in the mixture ranges from about 1/26 to about 2/1, andup to about percent of an additional blasting agent or additives knownin the explosives art.

The explosive composition contains up to about 90 percent of a blastingagent and/or additive such as, for example, additional inorganicoxidizing salts, fuels and sensitizers, thickening agents, densitycontrol agents and the like, in addition to the above defined mixture.

DETAILED DESCRIPTION OF THE INVENTION As indicated, the presentexplosive composition comprises at least from about 10 to percent sodefined mixture. Preferably the explosive composition comprises fromabout 10 to about 40 percent by weight of the mixture.

Also, the mixture preferably comprises about a stoichiometric amount ofsaid organic fuel and Ca(NO to produce N C0,. and H. .O upon combustionof the mixture. 1

The organic fuel component employed in the mixture comprises watermiscible organic compounds and mixtures thereof which contain at leastone functional group selected from the group consisting of =0, -'OH,

N, =N1-I, Nl-'I. S and SH and which form a stable liquid solution inwater at normal temperatures. Examples of groups of organic fuels whichcan be employed comprise certain amines, including primary andsecondary; amides; alcohols including both monoand polyhydric alcohols;alcohol ethers; carbohydrates (saccharides and polysaccharides);compounds which are hydroxy or'polyhydroxy derivatives of hydrocarbonsincluding monosaccharides and disaccharides, sulpho compounds includingsulphoamino and sulphoamido compounds, aldehydes .and various salts ofsuch compounds. Specific compounds include, for example, n-octylamine,sodium alkyl aryl polyether alcohol sulfonates such as the compound CH1,C(CHQ: CH C(CH;,)- (OCH CH J ,.Ol-I in which x has an average value ofSO Na about 20; N,N-dimethyl formamide, 1-hydroxy-2-methoxy-4-allylbenzene, fon'namide, dimethyl sulfoxide; ethylene carbonate; glycerol;acetonitrile; acetic acid, glyconitrile; ethylene glycol monomethylether; methanol; ethanol; furfuryl alcohol; diethylene glycol; sodiumacetate; hexamethylene tetramine; hexamethylene tetramine mono anddinitrate; acrylonitrile', acetamide; glycine; ammonium gluconate;acrylamide; N,N-dimethyl acetamide; ethylene glycol; propylene glycol;urea; thiourea; formaldehyde; acetadehyde ammonia; methylacetylcarbinol; acetone cyanohydrin; 2-hydroxybutylaldehyde; pentylene glycol;benzylamine; butylamine; .butyldiethanolamine; diacetone alcohol;diethylene-di-imide oxide ethanol; hexylene glycol; methyl glycerinate;3-methylpyridine; thiodiglycol; triethanol amine; benzyl hydrazinel,synthetic sugar likematerials, sugar, molasses, and mixtures ofcompatible compounds. Polymersmay also be employed as fuels and in someinstances they will also serve as a thickening agent. Suchpolymersinclude, for example, polyamides, celluloses, guar, polyols,polyalkylamines, polyethyleneimines and other water soluble polymerscontaining the previously defined functional groups.

Preferred water miscible organic fuels include lower alcohols, glycols,polyglycols, saccharides, amines or amides including, as examples,methanol, ethanol, ethylene glycol, propylene glycol, formamide,molasses, glycerol, mannitol, sorbitol and mixtures thereof.

By miscible it is meant that the organic fuel is normally soluble in theliquid phase of the mixture to the extent of at least about 2 percent byweight of the mixture.

The so defined mixture may be added to any of the blasting agents wellknown in the art to enhance certain characteristics thereof. Thus is maybe added to inorganic oxidizing salts other than calcium nitrateincluding, for example, ammonium, alkaline earth and alkali metalnitrates, sulfates, chlorates and perchlorates. Specific examples ofsuch salts include ammonium nitrate, sodium nitrate, ammoniumperchlorate, barium nitrate, ammonium sulfate, sodium sulfate, sodiumperchlorate, potassium perchlorate or mixtures thereof and the like. Theinorganic oxidizing salts may be employed in particulate form, insolution or both.

In addition the explosive composition can contain sensitizers and/orfuels to alter or improve certain explosive characteristics of thecomposition. Well known sensitizers and/or fuels normally employed ininorganic oxidizing salts based explosive compositions can be employedin the present invention. These fuels and sensitizers comprise, forexample, particulate metals, selfexplosives and non-explosive waterinsoluble carbonaceous fuels and/or others such as sulphur and mixturesof two or more of these materials. They are employed in amountssufficient to enhance the base explosive compositions in the mannerdesired. For example, metal may be employed in an amount to provide aweight ratio of metal to the base composition of up to 1/1 and more. Thekind and size of the metal particles will effect the explosivecomposition in several different ways as is well known in the art. Finermetal, e.g. 200 mesh tends to sensitize the explosive composition todetonation while coarser metal tends to increase the power of thecomposition when exploded, but with less sensitizing effect. The use ofsuch specific size metals is described in US. Pat. Nos. 3,307,986 and3,432,371. The teachings of these patents are specifically incorporatedherein by reference.

Particulate metals which can be employed include, for example, aluminum,magnesium, iron, silicon, titanium, aluminum alloys, silicon alloys,magnesium alloys, ferrosilicon, silicon carbide, ferrophosphorous, zinc,boron, and other like particulate metals which sensitize and/or functionas a fuel in the explosive. Of particular importance are the lightmetals, e.g. aluminum, silicon, magnesium, beryllium, alloys thereof andthe like. Generally the metals range in size from about 4 to about +325mesh, US. Standard Sieve Series. For metals which react with materialsin the explosive composition, e.g. nitrate solution, water, etc.,certain inhibitors known in the explosives art may be employed tostabilize the composition; as examples of such inhibitors are ammoniumor alkali metal phosphates and the like.

Self-explosives as used herein refer to those substances which, bythemselves, are generally recognized in the art as an explosive andwhich usually can be detonated with a No. 6 or 8 blasting cap. Examplesof selfexplosives which can be employed include organic nitrates, nitrocompounds and nitroamines such as TNT, pentaerythritoltetranitrate(PETN), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine, tetryl, nitro starch and explosive grade nitrocelluloseas well as mixtures of the aforesaid and other self-explosives. Theself-explosives can be employed in any of the conventional forms such asflake. pelleted, gelatinized or crystalline.

Examples of water insoluble carbonaceous nonexplosive fuels andsensitizers which can be employed include finely divided coal andcarbon, solid carbonaceous vegetable products such as corn starch, woodpulp, ivory nut meal and bagasse, organic liquids such as petrolicliquids, including hydrocarbon oils, crude oils, and crude oilfractions, fuel oils, fatty oils. vegetable oils and mixtures of two ormore of these water insoluble carbonaceous non-explosive fuels.

Any grade of calcium nitrate, e.g., anhydrous or hydrated, may beemployed in the present invention. Anhydrous grade, not containing anywater, or mono, di tri, tetra fertilizer grade, or any other hydratedform may be employed. When hydrated calcium nitrate is employed thewater of hydration is considered in calculating the water content of themixture. Thus a portion of the water present in the mixture may comefrom water of hydration, water may be added separately or a combinationof the two can be employed.

Thickening and/or gelling agents can also be employed in the presentcompositions. These agents are employed in amounts to provide athickened free flowing pumpable to very stiff practically immobilecomposition. The physical characteristics desired depend mainly on theultimate use of the explosive. For example, in water-containingboreholes very strong gels or viscous compositions are desired toprevent a leaching out and erosion of the explosive composition. Gellingand/or thickening agents are employed which will swell and/or can becrosslinked in the liquid system containing dissolved Ca(NO water, andthe water miscible organic fuel. Examples of suitable gelling andthickening agents include synthetic polymers, e.g. polyethers,polyesters, polyacrylamide, polyamines, starches, metal alcoholates,polysaccharides, wheat flour, galactomannans, gums, such as guar, karayaand the like. Specific thickening agents which may be employed includecellulose acetate, polyalkylene glycol, hydroxyalkyl cellulose, potatostarch, wheat starch, corn starch, carboxymethyl hydroxyethyl cellulose,methyl cellulose, polyethylenimine carboxymethyl cellulose, polyvinylalcohol, polyvinylpyrrolidone (PVP), sodium polystyrene sulfonate andthe like. It has been found that cellulosic materials, e.g.,carboxymethyl hydroxyethyl cellulose, methyl and ethyl cellulose, andthe like are preferred in the present invention. Examples of thickenerswhich provide a thickening and suspending of solids by their physicalpresence include magnesium oxide, asbestos fibers, cotton fibers, glassfibers, wood fibers and the like.

Various density control agents can also be employed in the presentinvention. These materials are employed to decrease the density of theexplosive and/0r sensitize the composition and/or alter the energyrelease of the explosive composition and/or provide compositions whichcan be more readily exploded under elevated pressures and/or lowtemperatures. Density control agents include void containing materials,gas generating compounds, gaseous bubbles stabilized with gum and thelike. Suitable void-containing materials include, for example, hollowspheres prepared from metals, clays, glass, therrnoplastics, resins andother like materials. Also naturally occurring void-containing materialssuch as ground corn cobs, bagasse, can be employed in the explosive. Thecarbonaceous thickening, gelling and density control agents also provideadditional fuel for the explosive composition. Suitable gas generatingcompounds include certain carbonates and the like.

The 'ia'riisasmahs of the resenfi'nviaaafishge from dry substances tovery thick or very fluid materials.

Exemplary of specific blasting agents which can be employed in thepresent invention include ANFO, and

those blasting agents taught in US. Pat. Nos. 3,307,986; 3,456,589;3,446,681; 3,432,371; 3.287;]89; 3,260,632; 3,124,495; 3,400,026;

3,397,097 and other like inorganic oxidizing salt based compositionsknown in the art.

The use of the mixture to prepare aqueousslarries permits thepreparation of slurries containing smaller amounts of water. This hasthe advantage of preparing slurries which remain more fluid at lowertemperatures.

One preferred composition of the present invention comprises thefollowing constituents as percent by weight: from about 5 to about 25percent by weight of calcium nitrate; from about to about 25 percent ofa water miscible organic fuel; from about 3 to about 8 percent of water,and from about 50 to about 85 percent of ammonium nitrate. Optionally upto about 60 percent by weight of a metallic fuel may be employed. Also,an effective amount of a thickening or gelling agent may be employed tostabilize and waterproof the explosive. Other inorganic oxidizing salts,as well as self-explosive sensitizers, density control agents and thelike may also be employed to alter various characteristics of theexplosive composition.

, One method for preparing the explosive composition comprisesdissolving ammonium nitrate in a water miscible organic fuel, preferablygelled or thickened, adding solid ammonium nitrate to the gelled orthickened mixture and then adding slaked or unslaked lime. The lime willreact in situ to produce Ca(NO water, and ammonia, giving a slurrycontaining the above-defined constituents. Other constituents which maybe added include, particulate metals, density control agents and thelike. For example, a slurry explosive is prepared as follows: A polarorganic liquid such as formamide is thickened with about 2 percent ofmethyl cellulose. To about 18 parts by weight of the thickened liquid isadded about 20 parts by weight of ammonium nitrate and the mix allowedto come to equilibrium, i.e. the thickened liquid becomes saturated withammonium nitrate. To the saturated thickened liquid is then added about56 parts by weight of additional ammonium nitrate and about 5 parts byweight of CaO or Ca(OH) The resulting slurry will contain about 1.6 or3.2 percent water (depending on whether CaO or Ca(OH is employed).Particulate metal such as aluminum may be blended into the slurry ifdesired.

*Na EDTA is the sodium salt of ethylenediaminetetracetic acid. All thecompositions contained about 6 percent water derived from thetetrahydrate of calcium nitrate. They were all observed to have good toexcellant fluidity at room temperature. The four compositions wereplaced in a deep freeze at 20F for about four hours. At the end of thistime period Mixes A and B were solid while mix C was still fluid. andmix D. although stiff. was still workable.

EXAMPLE 2 In this example a gram composition was prepared in thefollowing manner. To 16 grams of formamide was added 74 grams ofammonium nitrate and 10 grams of CaO. A reaction was evident withmoderate odor of ammonia observed. The resulting composition was veryfluid.

EXAMPLE 3 Four compositions were prepared containing the constituents,as percent by weight as set forth in the following table. 306 grams ofgelled forrnamide were first prepared for use in the composition. Theformamide was prepared by mixing 6 grams of methyl cellulose to 300grams of formamide and allowing the mixture to gel. A weighed amount ofeach composition was then tested in a standard small lead block test. Inthis test a weighed sample of the composition was placed in a smallcontainer and placed on top of a steel driving plate which was centeredover a cylindrical lead block supported by a heavy piece of steel as abase. The deformation, i.e. reduction in height, of the lead block, ininches, upon detonation of the composition is taken as a measure of thedetonability and brisance of the charge. The weight of each sampletested and the resultant deformation (AH) in inches is also set forth inthe table.

Prepared by dissolving 60 grams Nl-LNO; in 40 grams H 0 and thickeningwith 1 gram of guar gum EXAMPLE 4 In this example various amounts of acalcium nitrate dihydrate-formamide mixture was added to NH ,NO and NHNO -metal compositions and the resulting mixes tested in a standard leadblock test similar to that employed in the previous example. Thecompositions, densities of the composition and resulting lead blockdeformations (AH in inches) is set forth in the following table.

TABLE 111 V Particu- Density AH AH Composition No. NH NO; c NQ -zl-l o"Formamide* late* Al (gm/cc) (inches) Density All constituents aie shownas percent by weight of the total.

NO -2H O mixture improved the performance of both NH NO and Nl-LNO metalmixtures.

EXAMPLE 5 In this example various mixtures of Ca(NO -2l-l O andformamide were tested in a lead block test similar to that described inthe previous examples. The following table lists the compositions,density and deformation (AH in inches).

What is claimed is:

l. A method of preparing an explosive composition containing calciumnitrate, water and a liquid water miscible organic fuel which comprises:

a. preparing a mixture of ammonium nitrate and said liquid watermiscible organic fuel, and

b. reacting slaked or unslaked lime with said mixture of ammoniumnitrate and liquid water miscible organic fuel by mixing said limetherewith to form a mixture of calcium nitrate, water and liquid watermiscible organic fuel said slaked or unslaked lime being provided in anamount sufficient to provide the quantity of calcium nitrate desired insaid explosivc composition.

7' As demonstrated the addition of the formamide/CaC V 2. The method asdefined in claim 1 including thickening the ammonium nitrate and liquidwater miscible organic fuel prior to reacting it with the slaked orunslaked lime by adding a thickening or gelling agent thereto.

3. The method as defined in claim 2 wherein sufficient ammonium nitrate,slaked or unslaked lime. liquid water miscible organic fuel, andadditional water if necessary are mixed and reacted together to form amixture comprising from about 10 to about 100 percent by weight of amixture comprising from about 65 to about percent by weight of calciumnitrate. from about 15 to about 35 percent by weight of a liquid watermiscible organic fuel. and water in an amount to provide a weight ratioof water to calcium nitrate ranging from about l/26 to about 2/1.

4. The method as defined in claim 1 wherein sufficient ammonium nitrate,slaked or unslaked lime. liquid water miscible organic fuel, andadditional water. if necessary, are mixed and reacted to form anexplosive composition comprising from about 5 to about 25 percent byweight calcium nitrate; from about 10 to about 25 percent liquid watermiscible organic fuel; from about 3 to about 8 percent water; and fromabout 50 to about 85 percent by weight of ammonium nitrate.

5. The method as defined in claim 4 including thickening the ammoniumnitrate and liquid water miscible organic fuel by adding a thickening orgelling agent thereto prior to reacting it with slaked or unslaked lime.

6. The method as defined in claim 4 including mixing with said explosivecomposition during the manufacture thereof up to about 60 percent byweight of a particulate metallic fuel component.

2. The method as defined in claim 1 including thickening the ammoniumnitrate and liquid water miscible organic fuel prior to reacting it withthe slaked or unslaked lime by adding a thickening or gelling agentthereto.
 3. The method as defined in claim 2 wherein sufficient ammoniumnitrate, slaked or unslaked lime, liquid water miscible organic fuel,and additional water if necessary are mixed and reacted together to forma mixture comprising from about 10 to about 100 percent by weight of amixture comprising from about 65 to about 85 percent by weight ofcalcium nitrate, from about 15 to about 35 percent by weight of a liquidwater miscible organic fuel, and water in an amount to provide a weightratio of water to calcium nitrate ranging from about 1/26 to about 2/1.4. The method as defined in claim 1 wherein sufficient ammonium nitrate,slaked or unslaked lime, liquid water miscible organic fuel, andadditional water, if necessary, are mixed and reacted to form anexplosive composition comprising from about 5 to about 25 percent byweIght calcium nitrate; from about 10 to about 25 percent liquid watermiscible organic fuel; from about 3 to about 8 percent water; and fromabout 50 to about 85 percent by weight of ammonium nitrate.
 5. Themethod as defined in claim 4 including thickening the ammonium nitrateand liquid water miscible organic fuel by adding a thickening or gellingagent thereto prior to reacting it with slaked or unslaked lime.
 6. Themethod as defined in claim 4 including mixing with said explosivecomposition during the manufacture thereof up to about 60 percent byweight of a particulate metallic fuel component.